Pivot pins for a slack adjuster in a braking system and method of greasing the pins

ABSTRACT

A kit of parts to prevent seizing of yoke and link pins of slack adjusters in the braking system of highway tractors includes a replacement yoke pin and a replacement link pin. Both the replacement pins have a hexagonal head for gripping with a suitable wrench or socket tool to rotate the pins. The replacement yoke pin also includes a longitudinal bore which communicates between an outer surface of the shaft of the pin and a nipple at the head to introduce grease to the outer surface of the shaft of the pin. The combination of the longitudinal bore to introduce the grease and the hexagonal head for rotating the pin permits the grease to be thoroughly dispensed about the pin and thereby prevent seizing.

FIELD OF THE INVENTION

The present invention relates to a kit of parts and method of use thereof for greasing the pivot pins on a braking system slack adjuster.

BACKGROUND

Highway tractors for towing trailers typically include a slack adjuster in the braking system which multiples and transforms the linear force of the air actuator of the braking system into a rotation force or torque which is used to apply the foundation brake. The slack adjuster provides adjustment of clearance between the brake lining and drum to compensate for wear. The slack adjusters include pivoting mounting locations which are typically exposed to the elements adjacent wheels of the vehicle so as to suffer from corrosion and the like in use. Such corrosion is known to cause seizure of the pivoting mounts of the slack adjuster to cause potential malfunctions of the braking system. U.S. Pat. No. 6,135,242 describes components of a related braking system in which yoke pins of the slack adjusters include bores which permit grease to be introduced into the pivot joint to assist in deterring corrosion, however the pins have a round head which is difficult to grip when the pins become seized and no means are provided for spreading the grease throughout the joint of the pivot pin.

SUMMARY

According to one aspect of the present invention there is provided a greasable pivot pin comprising:

an elongate shaft having a smooth cylindrical outer surface;

a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft;

a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough;

a longitudinal bore extending through the shaft in a longitudinal direction thereof;

at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and

a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore.

According to a second aspect of the present invention there is provided a kit of parts for use on a slack adjuster of a braking system of a highway tractor; the kit of parts a yoke pin and a link pin, the yoke pin comprising:

an elongate shaft having a smooth cylindrical outer surface;

a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft;

a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough;

a longitudinal bore extending through the shaft in a longitudinal direction thereof;

at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and

a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore;

the link pin comprising an elongate shaft having a smooth cylindrical outer surface;

a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft; and

a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough.

According to a further aspect of the present invention there is provided a method of greasing a yoke pin in a slack adjuster, the method comprising:

providing a yoke pin comprising:

an elongate shaft having a smooth cylindrical outer surface;

a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft;

a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough;

a longitudinal bore extending through the shaft in a longitudinal direction thereof;

at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and

a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore;

inserting grease into the nipple;

gripping the head with a suitable wrench-like tool;

rotating the yoke pin about a longitudinal axis thereof.

The combination of a head of hexagonal cross section with a bore to introduce grease to the outer surface of the shaft produces the surprising benefit of permitting the grease introduced through the bore to be spread thoroughly about the shaft of the pin by gripping and rotating the pivot pin. Thoroughly spreading grease introduced into the joint of the pivot pin is key to effectively deterring corrosion and keeping the braking system in good order. The pivot pin may be readily sold as a kit with a link pin having a similar hexagonal head to also permit the link pin to be loosened by gripping with a suitable wrench tool.

The shaft of the yoke pin preferably has a diameter of ½ an inch while the shaft of the link pin preferably has a diameter of ¼ of an inch.

The head of both the yoke pin and the link pin may have a diameter of 9/16 of an inch and a thickness of ¼ of an inch for gripping by conventional wrench like tools.

There may be provided a pair of the transverse bores diametrically opposed from one another midway between the head and the transverse aperture of the yoke pin.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:

FIG. 1 is a side elevational view of a slack adjuster.

FIG. 2 is an end elevational view of the slack adjuster.

FIG. 3 is a perspective view of the yoke pin and link pin of the kit of parts.

FIG. 4 is a sectional elevational view of the yoke pin.

DETAILED DESCRIPTION

Referring to the accompanying drawings, there is illustrated a kit of parts generally indicated by reference numeral 10. The kit of parts includes a yoke pin 12 and a link pin 14 which are used on a slack adjuster 16 of the braking system of typical large vehicles including highway tractors for towing trailers and the like.

When the brakes of the vehicle are applied, the linear travel of the brake actuator's push rod 18 causes the slack adjuster to rotate the foundation brake cam shaft which in turn begins to force the brake shoes into contact with the drum. When the body 20 of the slack adjuster rotates, the yoke assembly 22 pivots on the yoke pin 12 causing the link 24 to be pulled upward. The teeth on the link 24 mesh with the adjuster mechanism pinion and as the link is pulled it travels first through its free play then the pinion is rotated. Rotation of the pinion is transmitted through the clutch to the worm and shaft which results in rotation of the worm gear 26 which in turn adjusts or repositions the brake cam shaft. When the foundation brake shoes contact the drum of the brake system, the cam shaft begins to resist rotation and friction between the worm gear and worm builds, preventing further rotation of the worm. Brake adjustment ceases at this point and further rotation of the body 20 will cause the pinion and clutch spring to slip. The free play between the link teeth and the pinion results in a predetermined lining to drum clearance.

The yoke pin 12 and the link pin 14 each include an elongate, non-threaded shaft having a smooth cylindrical outer surface 28. A head 30 is mounted at one end of the shaft which is hexagonal in cross section and larger in diameter than the diameter of the shaft.

The head 30 is supported at a head end 32 of the shaft opposite a locking end 34 forming a transverse aperture 36 therein for receiving a locking pin 38 to secure the pin in a mounted position. The transverse aperture 36 extends diametrically across the shaft perpendicularly to the longitudinal direction thereof for receiving the locking pin 38 therethrough similarly to conventional pin lock fasteners.

The heads 30 of both pins 12 and 14 are ½ inch thick to match the common thickness of various wrench-like tools. The pins are further arranged such that the heads have a similar diameter of 9/16 of an inch.

The yoke pin 12 is larger than the link pin and accordingly includes a shaft which is ½ inch in diameter as opposed to the shaft of the link pin which is only ¼ of a inch in diameter.

The yoke pin further includes a longitudinal bore 40 which extends from an open end at the head 30 to an internal end 42 terminating before the transverse aperture 36. A diametrical bore 44 lies perpendicular to the longitudinal bore in communication therewith to define a pair of transverse bores which meet the outer surface 28 of the shaft midway between respective ends of the shaft. A nipple 46 is mounted at the head of the yoke pin in communication with the longitudinal bore and accordingly the diametrical bore 44 for introducing grease from the nipple to the outer surface of the shaft.

In use the yoke pin and link pin of the kit replace the corresponding yoke and link pins of a slack adjuster on a braking system of a vehicle to assist in corrosion prevention thereof. For greasing, grease is introduced into the nipple 46 to be injected within the bore which the yoke pin is received. By gripping the hexagonal head with a suitable wrench tool rotation of the yoke pin about its respective longitudinal axis ensures that the grease is thoroughly spread about the outer surface of the shaft of the yoke pin. Gripping the hexagonal head of the link pin can be accomplished with the same tool due to the similar dimensions to the yoke pin such that rotation thereof acts to free corrosion and debris which may have accumulated at the outer surface thereof.

In further arrangements the greasable yoke pin with the hexagonal head may be provided by itself to produce advantageous results of spreading grease in pivot joints of various hardware requiring a pivot pin.

While one embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention. The invention is to be considered limited solely by the scope of the appended claims. 

1. A greasable pivot pin comprising: an elongate shaft having a smooth cylindrical outer surface; a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft; a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough; a longitudinal bore extending through the shaft in a longitudinal direction thereof; at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore.
 2. The pivot pin according to claim 1 wherein the shaft has a diameter of ½ an inch.
 3. The pivot pin according to claim 1 wherein the head has a diameter of 9/16^(th) of an inch.
 4. The pivot pin according to claim 1 wherein there is provided a pair of the transverse bores diametrically opposed from one another midway between the head and the transverse aperture.
 5. A kit of parts for use on a slack adjuster of a braking system of a highway tractor; the kit of parts a yoke pin and a link pin, the yoke pin comprising: an elongate shaft having a smooth cylindrical outer surface; a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft; a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough; a longitudinal bore extending through the shaft in a longitudinal direction thereof; at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore; the link pin comprising an elongate shaft having a smooth cylindrical outer surface; a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft; and a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough.
 6. The kit of parts according to claim 5 wherein the shaft of the yoke pin has a diameter of ½ an inch and the shaft of the link pin has a diameter of ¼ of an inch.
 7. The kit of parts according to claim 5 wherein the head of both the yoke pin and the link pin have a diameter of 9/16^(th) of an inch.
 8. The kit of parts according to claim 5 wherein there is provided a pair of the transverse bores diametrically opposed from one another midway between the head and the transverse aperture of the yoke pin.
 9. A method of greasing a yoke pin in a slack adjuster, the method comprising: providing a yoke pin comprising: an elongate shaft having a smooth cylindrical outer surface; a head mounted at one end of the shaft which is hexagonal in cross section and which is larger in diameter than the shaft; a transverse aperture extending through the shaft at an opposite end from the head for receiving a locking pin therethrough; a longitudinal bore extending through the shaft in a longitudinal direction thereof; at least one transverse bore communicating between the longitudinal bore and the outer surface of the bore; and a nipple supported on the head for communication with the longitudinal bore to introduce grease into the transverse bore at the outer surface of the shaft through the longitudinal bore; inserting grease into the nipple; gripping the head with a suitable wrench-like tool; rotating the yoke pin about a longitudinal axis thereof.
 10. The method according to claim 9 wherein the shaft has a diameter of ½ an inch.
 11. The method according to claim 9 wherein the head has a diameter of 9/16^(th) of an inch.
 12. The method according to claim 9 wherein there is provided a pair of the transverse bores diametrically opposed from one another midway between the head and the transverse aperture. 